Electronic devices, such as a tablet computer, can communicate with storage device of Serial ATA Advanced Host Controller Interface (AHCI) or storage device of Non Volatile Memory Express (NVME) via the PCI-Express. However, an electronic device with the PCI-Express protocol fails to identify the type of the storage device, thus the electronic device with the PCI-Express is not able to distribute cache space to other storage devices communicating with the electronic device, based on the different types of the other storage devices.